Focusing device for cinematographic apparatus



July 16, 1935. F. w. JACKMAN 2,008,020

FOCUSING DEVICE FOR CINEMATOGRAPHIC APPARATUS Filed NOV. l5, 1932 IN VEN TORI FREDNJHUKMHN.

ATTORNEY Patented July 16, 1935 PATENT .or-TICE FocUsING DEVICE Foa CINEMATO- GRAPITIC APPARATUS Fred W. Jackman, Beverly to Warner Bros. Pictures,

Hills, Calif., assignor Inc., New York, N. Y.,

a corporation of Delaware- Application November 15, 1932, Serial.No. 642,698

z claims. 1 (ci. :is-24) 'I'his invention relates to the art of photography and has to do with the making of composite motion pictures by the so-called translucent screen method.

An object of the invention is to overcome a certain dilculty which has been encountered when focusing a projector onto a translucent screen, for the projection of motion pictures, to be photographed, in conjunction with an action component, by a motion picture camera located on the opposite side of the screen.

At the present stime, when ,a cameraman-is focusing his camera to photograph the action and the projected background scene, he must telephone to the projectionist and direct him how to focus the projected picture, as the projectionist is unable to see the projected picture due to flare caused by light reflected from the screen. As will be readily understood, this phoning involves considerable inconvenience and loss of time.

'I'he present invention overcomes this diiculty by making it possible to focus the projector from a point adjacent the\camera.

This is accomplished by providing a motor mounted 'on the projector for eiecting the adjustment of the lens mount. The circuit of this motor is controlled by a switch located adjacent the camera, where it may be controlled by a camera operator.

For further details of the invention reference may bemade to the drawing, wherein:

Figure 1 is a front elevation of a lens mount of a preferred type. f

Figure 2 is a cross-section, with partsomitted for the sake of clarity, along the line 2 2 of Figure l.

Figure 3 is a diagrammatic view of a convenient circuit arrangement for controlling the motors used in this invention. 1

Figure 4 is a diagrammaticview of amotion lpicture camera and projector embodying this invention set up for photographing.

Referring in detail to the drawing, the camera I,

(Fig. 4) is provided with the usual lens 2 which' is focused to photograph an action component 3, located on a. suitable stage in front of a translucent screen 4. Action 3 may consist of an actor or a. plurality of actors or a setor any other form of tangible object. Translucentscreen 4 may be of that type having a cellulose base as described and claimed in my co-pending application, S. N.'

631,964, led September 7, 1932.

A projector 5 is located on the opposite side of the screen 4. 'I'he camera I and the projector 5 have a suitable electric interlock 6 for synchronous operation. Projector`-5 has a front wall `I supportinga lens barrel 66. A lens mount 8 ls mounted on the wall 1.

The mount 8 consists primarily of a split ring 9 adapted to t around the annulus of lens barrel 66. The ring 9 is tightened or loosened as desired, by a thumb screw I2, which passes` through al pair of lugs I3 and I4 mounted on either side of the slit in the ring 9. The bottom -o1 the ring 9 extends outwardly to form two recing 2| in the base plate I 8. A pinion gear 22 is Amounted on the screw 20, adjacent the base I8 and meshes with a second pinion gear 23 mounted on a shaft 24. Shaft 24 is journaled at one end in a bearing 25 mounted in the cross-arm 26 of the AU vshaped extension Il.

A ratchet gear 21 having a left hand ratchet is mounted on the shaft 24 adjacent lthe pinion 23. A second ratchet 28 having a right hand ratchet is mounted on the shaft 24 adjacent the bearing Screw is exf tended and journaled in a suitable bearing hous- 25, lso that when the ratchet 28 is turned, the \A lens ring 9 will be advanced, and when the ratchet 2'I is turned, the lens ring 9 will be retracted.

Mounted on the base I8 is`an electro-magnetic motor 29 which has an extending pawl arm 30, mounted o'n a contact armature 36. Pawl arm 30 engages ratchet Wheel 2l. A similar electromagnetic motor 32 is mounted adjacent motor 29. It has a pawl arm' 33 mounted on a contact armature 34. Pawl arm 33 engages ratchet 28. The motors 29 and 32 are exactly` similar and a description will be given of one of them, 29, as shown in Figure 3. I J

The motor consists of an electro-magnet 35 having a contact armature '36, normally held open fat contact 43 and closed at contact 4I as in Figure 3, by a spring 3'I. 'I'he electro-magnet 35 has a suitable magnetic winding 39. One terminal of the winding 39 is connected to a suitable source of potential, such as battery 40. The other terminal is connected to a contact 'arm 6l carried by the armature 36. A back contact 4I is located adjacent the contact arm 61 and connected in series with the battery 40. A switch 42 is l0- cated in the circuit between battery ll and contact di. The circuit between the battery 40 and the armature 36 is'branched and connected to back contact 4l and to front contact 43, these conatacts being located on opposite sides of the contact arm6l. Contact 63 is connected through a switch 63 to the circuit from switch 62. Contacts di and i3 complete the circuit through the winding 39 when the armature is released and attracted respectively. Switches 42 and M are remotely situated adjacent the camera operator.

The normal position of the apparatus is with both the switches l2 and $4 closed. Similarly the two corresponding switches provided for the solenoid-32 are closed, whereby the armatures 36 and 36 are held against their .respective front contacts, such as 43, by the solenoid's. In other Words, the pawl arms -and 33 attached to the armatures 33 and 36 are disengaged from their respective ratchets 21 and 28.

When the switch 4t is open, thereby opening the locking circuit for the winding 39, and the switch 42 is closed, or' when the same circuit conditions prevail for motor 32, the motors 29 and 32 will alternatively act as buzzers and rapidly .advance or retract the lens of theprojector 5, as

desired.

When the switch ill is closed, the switch l2 may beopened and closed at will and the armature 36 will move with a step by step motion as is Well understood'. When similar circuit conditions prevail for the motor 32, the armature 34 will also move with a stepby step motion and so the lens ring 9 may be slowly advanced or retracted as desired. y

Switches l2 and d@ are shown in Figure 4 tol gether with the switches 45 and 46 (for the sec- 'ond electro-magnetic motor) located on a suitable panel 'i adjacent thecamera l. These switches are connected by suitable circuits "i8 to the respective motors 29 and 32. Four contact terminals 53, 5t, 55, and 56, two for each oi' the.

electro-magnetic motors 29 and 32, are mounted on the base 6.

In the operation of this device when the camera operator wishes to change the focus of the projector 5, he opens one of either of the switches M or 45 which will rapidly advance or retract the lens ring 6 as desired until a rough focus has been obtained. He then opens and closes, as desired, either the switch. $2 or the switch d6, whereby the actuated motor will move with a step by step motion and the focus may be completed with a micrometer precision. A very accurate focus of the projector 5 may thus be obtained from a point remote therefrom with speed and convenience.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent is: y

- l. A focusing device for the lens of a motion picture projector comprising a bracket having a vertical flange and a horizontal portion, means for fastening said vertical ange to the front of the projector, said horizontal portion comprising spaced parallel guide rails adapted to receive shoes on a split ring adapted to hold a lens bar- -rel, a rotatable screw adapted to engage screw threads on said ring to move said ring, a counter shaft mounted on `said bracket, means for coupling said counter shaft to said screw, and means for rotating said counter shaft in opposite directions.

2. A focusing device for the lens of a motion picture projector comprising a bracket having a vertical flange and a horizontal portion, means for fastening said vertical flange to the front of the projector, said horizontal portion comprising spaced parallel guide rails adapted to receive shoes on a split ring adapted to hold a lens barrel, a rotatable screw adapted to engage screw threads on said ring to move said ring, a counter shaft mounted on said bracket, means for coupling said counter shaft to said screw, and means for rotat- 

